What is nakula veena?

"Nakula Veena" is not a recognized musical instrument or term in Indian classical music. It's possible there's a misunderstanding or a variation in the spelling.

Perhaps you meant one of the following:

* Nārada vīṇā: A large, ancient Indian stringed instrument with a long history and significant cultural importance. It is known for its rich and resonant sound.

* Vīṇā: A general term for a variety of plucked string instruments in India. It includes the Nārada vīṇā, the Saraswati vīṇā, and the Rudra vīṇā.

Please clarify your question if you meant something else, and I'll be happy to assist you further.